1. Field Of The Invention
This invention relates to miniature electro-mechanical relays and semiconductor devices, and more particularly, to apparatus for rapidly and accurately testing such relays and devices in production.
2. History Of The Prior Art
Electro-mechanical relays have been used in electronic circuits for as long as such circuits have been manufactured. Such relays utilize a mechanical connector which is opened and closed to make contact between two points in a electric circuit. Although many such relays have been replaced by electronic switches which may be of microscopic size and thus may be placed within the tiny circuits of modern electronics, many situations exist where the electrical performance of an electro-mechanical relay is superior to that of the electronic switch. For example, an electro-mechanical relay can achieve a fiat amplitude response well into the gigahertz frequency range and still have a response down to direct current. The power handling capabilities of an electro-mechanical switch greatly exceed those of electronic switches. For these and many other reasons, electro-mechanical switches are useful in many situations.
A number of small electro-mechanical relays are encapsulated in very small housings and are used in various products such as aircraft which require significant testing over a wide range of temperature and environmental conditions. The testing of these parts is quite stringent because failure of the relays could have significant effect on the product with which they are used. For example, certain of these relays are tested across temperature ranges which vary from minus 65 degrees centigrade to plus 125 degrees centigrade. They are tested while being subjected to intense atmospheric moisture. The relays are subjected to these and a number of other tests for extended periods of up to two hours. Other encapsulated electrical devices such as semiconductor devices often must be similarly tested.
In order to test the relays, it is necessary to position each relay in some sort of a special test assembly or socket which allows the relays to be isolated in environments in which the test conditions may be applied. These assemblies or sockets must be placed in heating and refrigerating atmospheres and immersed in moisture for extended periods while various electrical tests are carried out. The extreme environmental conditions to which these sockets are subjected has made the sockets subject to drastic failure rates. For example, it has been typical for certain testing sockets to begin failing after as few as forty-three relays have been tested. Typically, such test sockets have been hand made by a process which requires approximately thirty hours of skilled labor to produce each socket. Since approximately 10,000 relays must be tested each day, the expense of testing and of constructing new sockets has made the relays overwhelmingly expensive.